The proposal consists of four parts: (1) A preliminary quantitative study of the so-called "barrel" field of the mouse somatosensory cortex in normal adult animals and in mice from which groups of mystacial vibrissae were removed shortly after birth. In this part of the work we hope to determine the optimum conditions for Golgi impregnation and to evaluate a number of computer-based methods for measuring a variety of neuronal parameters (e.g., lengths of branching patterns of dendrites, numbers of dendritic spines, etc.). (2) A quantitative study of the normal growth of projection and short axon cells in the dorsal lateral geniculate nucleus (LGN) and of pyramidal and stellate cells in the striate cortex of macaque monkeys (Macaca mulatta). (3) An examination of the effects of unilateral and bilateral eyelid closure early in postnatal life on the growth of cells in the LGN and on the dendritic morphology of pyramidal and stellate cells in the striate cortex, using a computer-controlled microscope and an acoustical data tablet. The extent of the cortical projection of normal and deprived cells in lamina 6 of the LGN will also be studied, using an automated method for quantitative autoradiography in the tracing of axonal connections. (4) The development of a series of new computer programs and associated hardware for the quantitative analysis of morphological data, including programs for the counting and graphic display of dendritic spines, for grain counting in autoradiographs, and for classifying neurons on a metric basis. Bibliographic references: Woolsey, T. A., Dierker, M. L. and Wann, D. F. Mouse Sml cortex: Qualitative and quantitative classification of Golgi-impregnated barrel neurons. Proc. Nat. Acad. Sci. U.S.A., 72: 2165-2169, 1975. Pasternak, J. F. and Woolsey, T. A. The number, size and spatial distribution of neurons in lamina IV of the mouse Sml neocortex. J. comp. Neurol., 160: 291-306, 1975.